1. Field of the Invention
The present invention relates to an image stabilizer which stabilizes image blurred by vibration or the like at the time of shooting; a lens device which has the image stabilizer; and an imaging apparatus such as a digital still camera or video camera, incorporating the lens device.
2. Description of the Related Art
In recent years, performance of an imaging apparatus such as a digital still camera and a video camera has been improved remarkably, and it became possible for anyone to easily shoot still pictures and moving pictures with high image quality and with high efficiency. Improved efficiency of such an imaging apparatus owes to high performance of an imaging apparatus such as a lens, a CCD (solid-state imaging device), and an image processing circuit.
However, even though the lens, the CCD and the like can be made higher in performance, if camera shake or vibration is caused by photographer's hands holding a camera (imaging apparatus), blurring occurs in images with high resolution and shot images are blurred. Therefore, some relatively expensive cameras are provided with an image stabilizer capable of stabilizing images blurred by camera shake and the like upon image pickup. However, cameras that require such image stabilizer are not professional-level cameras, and it is to be understood that image stabilizers are indispensable to consumer cameras for a large number of amateur photographers with less shooting experience.
Further, in general, a demand for smaller and lighter cameras (imaging apparatuses) is strong and most of photographers like cameras which are light in weight and easy to carry. However, since an image stabilizer in related art is comparatively large in size, when such large image stabilizer is mounted on a camera body, the whole of the camera becomes large in size, which is against a demand for making cameras smaller in size and lighter in weight. In addition, image stabilizers in related art require a large number of components, thereby causing a problem in which a cost of cameras increases as the number of components increases.
Japanese Patent Application Publication No. H3-186823 discloses a first example of an image stabilizer of this kind in related art, for example. In this Patent Literature, there is described one relating to a vibration-prevention device provided in a camera or the like, which detects camera shakes relatively low in frequency and uses the detected results as information for the prevention of image blurring, thereby preventing image blurring. The vibration-prevention device described in this Patent Literature (hereinafter referred to as “a first related-art example”) is a vibration-prevention device for a camera, including: a correcting optical mechanism, a vibration detector and a vibration-prevention controller. The correcting optical mechanism is provided inside a lens barrel holding a lens group and deviates the optical axis of the lens group. The vibration detector detects vibration applied to the lens barrel. The vibration-prevention controller prevents vibration by driving the correcting optical mechanism based upon a signal from the above-described vibration detector. The correcting optical mechanism has: a correcting lens, a fixing frame, a first holding frame, a second holding frame, first and second coils, first and second drivers, and first and second position detectors. The fixing frame fixes the correcting lens. The first holding frame holds the fixing frame such that the fixing frame can be moved in the first direction different from the optical axis direction of the lens group. The second holding frame holds the first holding frame such that the first holding frame can be moved in the second direction different from the optical axis direction and the first direction, and is fixed to the lens barrel. The first and second coils move the first and second holding frames in the first and second directions, respectively. The first and second drivers are formed of first and second magnetic field generating members facing the first and second coils. The first and second position detectors detect the amount in which the fixing frame and the first holding frame are moved in the first and second directions. At least either the first and second magnetic field generating members or the first and second position detectors are provided in a fixed member including the second holding frame, fixed to the lens barrel.
According to the vibration-prevention device with the structure described in Japanese Patent Application Publication No. H3-186823, there can be expected such effectiveness that the vibration-prevention device responds up to high-frequency vibration without increasing the cost and requiring a large space (refer to “Effect of the Invention”).
Japanese Patent Application Publication No. 2000-258813 discloses a second example of an image stabilizer in related art, for example. In this Patent Reference, there is described one relating to an image stabilizer used for optical equipment and a lens barrel using the image stabilizer. The image stabilizer described in this Patent Reference (hereinafter referred to as “a second related-art example”) is an image stabilizer which stabilizes images by moving part of a imaging lens to the inside of a surface perpendicular to an optical axis, including: a lens holding frame, a first guide, a second guide, a first driver, a second driver, and a position detector. The lens holding frame holds a correcting lens. The first guide guides the lens holding frame to move in a first direction within a surface perpendicular to the optical axis. The second guide guides the lens holding frame to move in a second direction perpendicular to the first direction. The first driver and second driver drive the lens holding frame in the first and second directions, respectively. The position detector detects the position of the correcting lens. In this image stabilizer, the first guide and the second driver, or the second guide and the first driver are arranged to partially overlap, when seen from an optical axis direction.
According to the image stabilizer with the structure described in Japanese Patent Application Publication No. 2000-258813, the following effectiveness may be obtained, for example. Specifically, the width and height of the stabilizer can be reduced by arranging a guide shaft for moving a correcting lens, and a coil or magnet for driving the correcting lens such that a pitch moving mechanism and a yaw driver, or a yaw moving mechanism and a pitch driver are arranged to overlap when seen from an optical axis direction (see paragraph [0032]).
However, regarding the aforementioned first and second related-art examples, a holding frame having a correcting lens is guided and supported in a movable manner in a first direction and second direction perpendicular to each other; and the guiding and supporting mechanism includes a combination of a shaft and a bearing portion, two pairs of which make one set. In this case, there may need some gap between the shaft and bearing portion of each combination in order for the holding frame to move, which causes a problem of looseness when moving, and the looseness not only makes smooth motion difficult but also makes the position of the correcting lens unstable.
Further, in the case of an image stabilizer apparatus being used with an optical axis of a correcting lens directed in a horizontal direction, in other words, in an imaging apparatus whose lens device, in which an optical axis of a lens system is directed in a horizontal direction, has the aforementioned image stabilizer apparatus, a holding frame holding the correcting lens is used with its moving direction set in the gravitational direction. Therefore, a moving frame may be required to be held at a predetermined height by supplying power to a coil all the time. As a result, there is an increase in the consumption of power, hence, causing the power consumption to increase in a battery and the temperature inside an apparatus to rise by the heat of an actuator and the like.